TableFS - a table filesystem implemented in lua tables

tfs.lua

----
-- Table FS
----
-- an unix-like filesystem simulation on lua tables
-- by Severak 2012
-- license: WTFPL
----

-- documentation will come later....
function tDir(t)
	for k,v in pairs(t) do
		if type(v)=="table" then
			v[".."]=t
		end
	end
	t["."]=t
	return t
end

function TableFS(tree, startPath)
	startPath = startPath or "/"
	local state={}
	local tfs={}
	
	function walk(d, path)
		local current=d
		for name in path:gmatch("([^/]+)") do
			if type(current[name])=="table" then
				current=current[name]
			elseif current[name] then
				return current[name]
			else
				return nil
			end
		end
		return current
	end
	
	state.root=tree
	state.wd=walk(state.root,startPath)
	
	tfs.load=function(path)
		if string.sub(path,1,1)=="/" then
			return walk(state.root, string.sub(path,2))
		else
			return walk(state.wd,path)
		end
	end
	
	tfs.save=function(path,data)
		local a,b=string.match(path,"(.+)/([^/]+)")
		local dir=nil
		local name=nil
		if a and b then
			dir=tfs.load(a)
			name=b
		else
			dir=state.wd
			name=path
		end
		dir[name]=data
	end
	
	tfs.dir=function(path)
		path=path or "."
		local cd=tfs.load(path)
		if not (type(cd)=="table") then
			error(string.format("%s is not dir"),path)
		end
		local listing={}
		for k,v in pairs(cd) do
			listing[#listing+1]=k
		end
		table.sort(listing)
		local i=0
		local n=#listing
		return function()
			i=i+1
			if i <= n then return listing[i] end
		end
	end
	
	tfs.chdir=function(path)
		local newDir=tfs.load(path)
		if newDir then
			if type(newDir)=="table" then
				state.wd=newDir
				return true
			end
			return nil, "This isn't dir." 
		end
		return nil, "Path goes to nowhere"
	end
	
	tfs.mkdir=function(name)
		if state.wd[name] then
			return nil, "Directory already exists."
		else
			state.wd[name]={}
			state.wd[name][".."]=state.wd
			state.wd[name]["."]=state.wd[name]
		end
	end
	
	tfs.pwd=function()
		curr=state.wd
		local names={}
		while curr[".."] do
			prev=curr
			curr=curr[".."]
			for k,v in pairs(curr) do
				if v==prev then
					table.insert(names,1,k)
				end
			end
		end
		return "/" .. table.concat(names,"/")
	end
	
	return tfs
end